Safety switch

ABSTRACT

A safety switch has a key (1) which, when inserted into and removed from a key channel (9), forcibly rotates a cam plate (7) and so switches over the switch. The safety switch further has an interlocking device for the cam plate (7) which is disposed adjacent the latter, can be forcibly released by the key (1) when it is introduced into the key channel (9) and has at least one locking member (21) which can be displaced in translation and, in its locked position, engages in an interlocking manner with a housing disposed adjacent the cam plate (7). The locking member (21) can be displaced into the released position by the key (1) by means of an actuating member (15) which is moveable together with the locking member (21) and is integral therewith. The part of the actuating member (15) which projects into the key channel (9) in the locked position is connected to the locking member (21) by means of a material section which is laterally guided past the axis of rotation (6).

BACKGROUND OF THE INVENTION

In a known switch of this type, the locking member is constructed as ametallic, longitudinally displaceable locking pin which, in the lockedposition, engages a little in a transverse bore of a plate arranged nextto the cam plate and constructed with the latter in one piece. Ametallic actuating pin is arranged as actuating member in thistransverse bore, which is open with a reduced cross-section towards thekey channel. In the locked position, the locking pin keeps the actuatingpin in a position in which the latter projects into the key channel.When the key is inserted into the key channel, it must firstly displacethe actuating pin so far that the locking pin no longer engages in thebore. Since the key rotates the cam plate after the unlocking, theactuating pin no longer bears against the locking pin in the releaseposition. In order, nevertheless, for both the actuating pin and thelocking pin to retain their positions, corresponding bearing surfacesmust further be provided for the two pins. The known safety switch istherefore relatively complicated.

OBJECTS AND SUMMARY OF THE INVENTION

It is the object of the invention to provide a more cost-effectivesafety switch. This object is achieved by a safety switch having thefeatures described and claimed herein.

Owing to the fact that the part of the actuating member projecting intothe key channel in the locked position is connected to the lockingmember via a material part guided laterally past the axis of rotation ofthe cam plate, the actuating member can be constructed in one piece withthe locking member, as a result of which the costs are considerablydiminished already purely by the reduced number of the individual partsto be produced and assembled.

The actuating member is preferably constructed as a sliding member whichlies in a plane parallel to the cam plate and is provided with a cutoutfor passage of the axis of rotation. The expenditure for guiding such asliding member is very low. This applies particularly whenever thecutout is constructed as an elongated hole having a width which iscoordinated with the diameter of the axis of rotation, because then thesliding member can be guided by the axis of rotation.

The locking member is preferably formed by a stop for a stop surface ofthe receptacle, which is formed by a material part provided on the sideof the cam plate facing the sliding member. This material partpreferably takes the form of a plate into which there penetrates fromthe circumferential surface a slot-like recess one edge of which formsthe stop surface. Such a receptacle can be produced verycost-effectively, since it can also be open in the axial direction.

In the case of a receptacle in the form of a slot-like recess, the stopwhich forms the locking member preferably has a tooth-like form. Alocking member constructed in this way also contributes to the fact thatthe component forming the locking member and the actuating member cantake a form which is simple and cost-effective.

Since the actuating member has at least one material part guidedlaterally past the axis of rotation, the locking member could lie in theplane defined by the actuating member. In a preferred embodiment,however, the locking member is arranged next to the actuating member onthe side thereof facing the cam plate, in radial alignment with thematerial part forming the receptacle.

A minimum of individual parts is achieved when the material part formingthe receptacle is constructed in one piece with the cam plate and theaxis of rotation thereof.

Furthermore, on grounds of cost, in a preferred embodiment both the camplate with the material part forming the receptacle and the axis ofrotation, as well as the actuating member and the locking memberconstructed in one piece with it consist of plastic. Such plastic partscan be produced very cost-effectively.

To the extent that a second locking member with an associated actuatingmember is provided for safety reasons, the said members are constructedon grounds of cost like the first locking member and the actuatingmember thereof, respectively. Furthermore, the receptacle assigned tothe second locking member is also constructed like the receptacleassigned to the first locking member.

DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below with the aid of an exemplaryembodiment represented in the drawing, in which

FIG. 1 shows a side view, represented partially cut away, of theexemplary embodiment with associated key,

FIG. 2 shows another, second, side view, represented likewise partiallycut away, of the exemplary embodiment, and

FIG. 3 shows a section along the line III--III of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A safety switch, which can be operated only by means of an associatedkey 1, contains in a main part 2 of its housing, which consists ofplastic, a switch (not represented) which is operated by means of aplunger 3 which is arranged in the housing in a fashion capable oflongitudinal displacement. A head part 5, which can, instead of beingarranged in the position represented in FIGS. 1 and 2, also be arrangedrotated by 90° with respect to the main part 2 about the longitudinalaxis of the plunger 3, is fastened by means of screws 4 to one end faceof the main part 2 of the housing.

Rotatably mounted in the head part 5 with an axis 6 of rotationextending at right angles to the longitudinal axis of the plunger 3 is acam plate 7 which is aligned with the dome-shaped end, which pointstowards it, of the plunger 3. This end of the plunger 3 is held by meansof a spring (not represented) bearing against the control cam 8 formedby a part of the circumferential surface of the cam plate 7. A segment7' of the cam plate 7 whose lateral surface does not form the controlcam 8 projects into a key channel 9 which penetrates the head part 5transverse to the longitudinal direction of the axis 6 of rotation. Agroove 10 of the cam plate 7, which is provided between one end of thesegment 7' and that of the segment forming the control cam 8, serves toreceive a transverse web 1' of the key 1, which separates a firstlongitudinal slot 11 of the key 1 from a second longitudinal slot 11'extending up to the front end of the said key. The two longitudinalslots 11 and 11' have a width measured transverse to the longitudinaldirection of the key 1 which is greater than the thickness, measured inthe axial direction, of the cam plate 7. The latter can therefore engagein the first longitudinal slot 11 and the second longitudinal slot 11'.

A plate-shaped material part 12 is integrally formed on the cam plate 7,on both sides thereof. These two identically constructed material parts12 form together with the cam plate 7 and the axis 6 of rotation asingle-piece component made from plastic. As FIG. 1 shows for onematerial part 12, they both have a slot-like recess 13 which is openboth radially outwards and in the axial direction and which forms withone of its edges a stop surface 14 extending approximately radially.

One sliding member 15 each is arranged in the head part 5 in a fashioncapable of being displaced in the longitudinal direction of the plunger3 on each side of the cam plate 7 immediately next to the plate-shapedmaterial part 12 respectively present here. Apart from their end zonepointing towards the main part 2 of the housing, the two identicallyconstructed sliding members 15 have the form of a flat rail which liesin a plane parallel to the cam plate 7. As FIG. 3 shows, in particular,the sliding member 15 is penetrated in the middle by an elongated hole16 which extends in the direction of displacement and whose width isadapted to the diameter of the axis 6 of rotation, as a result of whichthe sliding member 15 is guided through the axis 6 of rotation. However,the head part 5 is provided in the exemplary embodiment with oneadditional, slot-like guide 17 each for the two sliding members 15. Onepreloaded helical spring 18 each, of which one end section is receivedby a blind bore in the end zone of the sliding member 15, attempts tohold the sliding member 15 in the locked position, represented in FIGS.1 to 3, in which its end section averted from the main part 2 of thehousing projects into the key channel 9. As is to be seen from FIG. 3,above all, this end section forms two ramps 19 and 20 inclined inopposite directions. The key 1 runs against one 19 of the ramps uponinsertion into the key channel. The other ramp 20 is required becausethe two sliding members 15 are of identical construction and arearranged in mirror-image fashion relative to the cam plate 7 in the headpart 5.

On the side, facing the cam plate 7, of the end zone of the slidingmember 15, a locking member 21 is integrally formed like a tooth whichpoints in the radial direction against the axis 6 of rotation and isaligned with the plate-shaped material part 12, that is to say lies inthe same plane as the latter. The sliding member 15 forms the actuatingmember for the locking member 21. As FIG. 1 shows, in its lockedposition the locking member 21 engages in the recess 13 of the assignedplate-shaped material part 12 in such a way that one of its edges bearsagainst the stop surface 14, and its head surface bears against the edgeof the recess 13 which adjoins the stop surface 14. In its lockedposition, the locking member 21 therefore prevents the cam plate 7 frombeing capable of rotation, specifically in a self-closed fashion for thedirection of rotation for the purpose of switch operation, that is tosay in an anticlockwise sense in the case of a direction of view inaccordance with FIG. 1, since in the case of this direction of rotationthe plunger 3 runs from the highest point of the control cam 8 to thelowest point, which is adjoined by a shoulder 8' which prevents furtherrotation.

When the key 1 is inserted into the key channel 9, it initially runsagainst the ramp 19 or 20 of the two sliding members 15, as a result ofwhich the latter are displaced so far against the main part 2 of thehousing that the locking member 21 releases the associated stop surface14. The transverse web 1', which enters the groove 10, can now rotatethe cam plate 7, as a result of which the plunger 3 comes to bearagainst the lowest section of the control cam 8, the consequence beingthat the switch is closed. In this rotary position (not represented) ofthe cam plate 7, the two locking members 21 are held in the releaseposition by the key 1.

When the key 1 is withdrawn from the key channel 9, the cam plate 7 ispositively rotated, specifically in the clockwise sense in the case of adirection of view in accordance with FIG. 1, the consequence being thatthe plunger 3 is positively moved against the switch operated by it, theconsequence being positive opening of this switch. When the key 1 hasleft the ramp 19 or 20, operated during insertion, upon being withdrawnfrom the key channel 9, it releases the two sliding members 15. Thehelical springs 18 then again push the two sliding members 15 into thelocked position, in which each of the two locking members 21 bearsagainst the assigned stop surface 14.

Both the production costs and the outlay on assembly are very low,because the safety switch comprises a minimum of individual parts which,in addition, are simple to assemble, specifically, apart from thehousing and the screws 4 connecting two parts thereof together, theswitch with the plunger 3, the component comprising the cam plate 7, theaxis 6 of rotation and the plate-shaped material parts 12, the twosliding members 15, each forming one of the locking members 21 and theactuating member thereof, and the two helical springs 18.

Although certain presently preferred embodiments of the presentinvention have been specifically described herein, it will be apparentto those skilled in the art to which the invention pertains thatvariations and modifications of the various embodiments shown anddescribed herein may be made without departing from the spirit and scopeof the invention. Accordingly, it is intended that the invention belimited only to the extent required by the appended claims and theapplicable rules of law.

What is claimed:
 1. Safety switch comprising:a) a switch housingincluding a switch; b) a plunger, arranged in the switch housing in afashion capable of displacement in its longitudinal direction againstthe force of a spring, for actuating said switch arranged in the switchhousing, c) a cam plate, which is mounted in the switch housing with anaxis of rotation extending at right angles to the longitudinal axis ofthe plunger, and against whose lateral surface, which forms the controlcam, the plunger bears, d) a key channel in the switch housing, intowhich the cam plate projects, e) a key which upon being inserted in andupon being withdrawn from the key channel positively rotates the camplate about its axis of rotation and in so doing switches over theswitch, f) a self-closed locked device, arranged next to the cam plateand capable of being positively released by means of the key uponinsertion into the key channel, for the cam plate, having at least onelocking member which can be displaced in a translatory fashion and whichengages in a self-closed fashion in its locked position with areceptacle arranged next to the cam plate and can be displaced by thekey into the release position, g) an actuating member constructed in onepiece with the locking member and projects into the key channel in thelocked position, wherein the part of the actuating member which projectsinto the key channel in the locked position is connected to the lockingmember via a material part guided laterally past the axis of rotation.2. Safety switch according to claim 1, wherein the actuating member isformed by a sliding member which lies in a plane parallel to the camplate and is provided with a cutout for passage of the axis of rotation.3. Safety switch according to claim 2, wherein the cutout is constructedas an elongated hole (16) having a width which is coordinated with thediameter of the axis (6) of rotation.
 4. Safety switch according toclaim 3, wherein the locking member is constructed by a stop for a stopsurface of the receptacle, which is formed by a material part providedon the side of the cam plate facing the sliding member.
 5. Safety switchaccording to claim 4, wherein the material part provided next to the camplate is formed by a plate, and the stop surface is formed by an edge ofa slot-like recess which penetrates into the plate from thecircumferential surface thereof.
 6. Safety switch according to claim 5,wherein the stop of the locking member is of tooth-like construction. 7.Safety switch according to claim 6, wherein the locking member isarranged next to the actuating member on the side thereof facing the camplate, in radial alignment with the receptacle.
 8. Safety switchaccording to claim 7, wherein the material part forming the receptacleis constructed in one piece with the cam plate and the axis of rotation.9. Safety switch according to claim 8, wherein both the cam plate aswell as the actuating member are plastic.
 10. Safety switch according toclaim 9, wherein a second locking member with an associated actuatingmember, which are constructed like the first locking member and theactuating member thereof, respectively, are arranged next to the camplate on the side thereof averted from the first locking member, and inthat the second locking member is assigned a second receptacle which isarranged next to the cam plate on the side averted from the firstreceptacle and is constructed like the first receptacle.